Overheating!

This has been a nightmare for me. During the summer my 91 535i used to overheat even when idling and soon, sure enough the headgasket was blown. So i changed the headgasket, the radiator (the neck connecting to the hose was broken), the waterpump (leaking coolant), thermostat, fan clutch...I also had a mechanic check the tube that runs along the left side of the panel, from the coolant tank to the radiator, he said it was fine. Now it doesn't overheat while idling but the indicator goes over the halfway mark while driving.

Does anyone know what the problem might be? Also, an easy way to check it (no money to take it to the mechanic at the moment).

Has the cooling system been bled properly? - these cars can be a nightmare to bleed, and it's easy to leave a pocket of air in the heater matrix & pipes to it. Do your heaters work OK?

Cheers,

Shaun

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Originally Posted by leetsauce4000

This has been a nightmare for me. During the summer my 91 535i used to overheat even when idling and soon, sure enough the headgasket was blown. So i changed the headgasket, the radiator (the neck connecting to the hose was broken), the waterpump (leaking coolant), thermostat, fan clutch...I also had a mechanic check the tube that runs along the left side of the panel, from the coolant tank to the radiator, he said it was fine. Now it doesn't overheat while idling but the indicator goes over the halfway mark while driving.

Does anyone know what the problem might be? Also, an easy way to check it (no money to take it to the mechanic at the moment).

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Mine sits a needle to the right of the halfway mark. Is that what you're talking about? How far past does your's go?

I'm assuming that you did the head gasket work yourself. Were the head and block checked for warping and cracks? Were the bolt holes cleaned out prior to reinstalling the head?

best, whit

No I didn't do the headgasket myself. I took it to a mechanic and he sent it to a machine shop and they said the cylinder head was fine. My heater works fine, I think, you can't really feel it until you turn the knob up to 3 or 4.

My needle went past 3/4 (almost to the red) last time it overheated ( didn't turn on heater to test the new fan clutch).
How do you bleed the system?

When the car is filled with coolant, the heat should be turned on "full" to activate the auxiliary water pump, which will move coolant through the heater core and help remove air.

I mean, unless the water pump/tstat/radiator are defective, and the pisser line is working correctly, I wouldn't be surprised to find that the shop that did the work didn't correctly reinstall the head. It's relatively common for a shop to not clean out the bolt holes, or incorrectly torque the head bolts. It usually results in something cracking. Check the coolant for signs of oil globs, and the oil for signs of coolant. Or, have a compression test done (still might not show a fine crack that only starts doing its thing on a warm engine).

But check the pisser, first. Do a search on it -- we all talk about it a lot ;)

best, whit

they compression tested it

My brother also installed a performance chip a year or so ago (dunno what kind), could that have anything to do with the overheating?

D I D Y O U B L E E D I T?

sounds like your whole nightmare issue has transpired due to lack of maintenance. Hoses, belts, waterpumps, thermostats are COMMON maintenence items not something that needs attending to when it goes bad.

Not to get on you but for you to look through your system and try to see what the problems are...IE: you replaced the head and its still over heating....HELLO? somethings still wrong and maybe it wasnt the head at all (well probably after an over heat procudure).

Quote:

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Originally Posted by leetsauce4000

My brother also installed a performance chip a year or so ago (dunno what kind), could that have anything to do with the overheating?

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It's not the chip (I very much doubt it anyway). You do know how to bleed the cooling system don't you?

LOL...did anyone mention the bleeding procedure?

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Originally Posted by uscharalph

It's not the chip (I very much doubt it anyway). You do know how to bleed the cooling system don't you?

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What does "bleed" mean?!?! How do you do it?

To bleed is to remove air from the system. Air prevents movement of the coolant/water mixure, thereby hindering cooling.

On the M30, the bleed screw lives at the top of the thermostat housing. It's pretty close to the highest point in the system, hence pretty much where air congregates. When filling a system with fresh coolant (be sure to use BMW Cool Blue, other/generic coolants are suspect), the bleed screw should be cracked open to allow the air to escape. If it's not, air stays in the system. Some air will be in there (maybe even trapped in the thermostat cover) regardless, which is why it needs to be bled out with the car running. With the expansion tank full and the cap off, start the car and open the bleed screw. Close it when a steady stream of fluid comes out, no air. Actuate the throttle and look in the expansion tank -- check for a steady stream of coolant returning via the pisser. No stream? Bleed some more, actuate the throttle some more. Don't overrev a cold engine -- keep it somewhere below 3k rpm. Once it's pissing, close the expansion tank and start driving the car/watch the temp gauge. An 88 degree tstat should keep the gauge at 12o. If the gauge goes above that, pull over immediately and bleed it -- if air comes out, get it all out. If coolant comes out and not air, shut off the car -- there's some other problem.

Also, the heat should be on high/full blast throughout the entire procedure.

Also, there's a good chance that the tstat itself, among other things, is fried if the car has been overheated.

The M30 isn't hard to bleed. I used to think it was a major pain in the ass.

best, whit

Crap...my mechanic put in generic coolant, I think it's blue though. Should I drain it? Also, just to double check, by "expansion tank," you mean the tank where you actually pour in the coolant, right? Does anyone have a picture of a pisser?

Thank you so much

the pisser goes from the expansion tank forward to the radiator.

"expansion tank," you mean the tank where you actually pour in the coolant, right?

That's it!

Thanks a lot guys. I very busy during the week but I'll try to bleed it during the weekend and tell you how that goes!